Scientists solve Knut death riddle

Scientists say they can now explain what happened to Knut, the famous polar bear that drowned at Berlin Zoo in 2011.

A new investigation has shown that he had a type of autoimmune inflammation of the brain that is also recognised in humans.

Knut experienced a seizure and collapsed into his enclosure's moat - right in front of the many zoo visitors who had come to see him - and never regained consciousness.

Researchers hope the new knowledge about his condition can help both human and animal sufferers in the future.

Prof Alex Greenwood, from the Leibniz Institute for Zoo and Wildlife Research, told our correspondent Jonathan Amos what had been discovered.